1. Field of the Invention
The present invention relates to the field of manufacturing by replication of a master pattern. More specifically, the invention relates to roll-to-roll replication of high aspect ratio three-dimensional microstructures from an image drum cylinder onto a continuous band of curable liquid adhesive in a process herein called PALM.
2. Background Art
In the present invention a liquid adhesive is applied, using a roll-to-roll technique to a drum having a microstructure pattern that is to be replicated onto a rolling flexible sheet or substrate. There are numerous prior art patents which disclose this type of replication process. By way of example, the assignee hereof has obtained U.S. Pat. Nos. 5,735,988 and 5,922,238 for replicating optical diffusers with shallow relief patterns. Others have disclosed similar replication processes for creating microcup patterns for manufacturing LCD displays. See for example U.S. Pat. Nos. 6,933,098; 6,930,818; and 6,672,921. There are also numerous issued U.S. Patents relating to roll-to-roll replication processes for fabricating retro-reflective sheeting and the like such as U.S. Pat. Nos. 5,763,049 and 5,691,846. However, such prior art relates generally to either relatively low profile, small relief patterns with structures having peak heights of less than about 5μ meters or to higher relief structures having very regular and thus highly predictable relief patterns.
However, there is a need for employing such low cost, high yield replication processes for fabricating deep relief, large profile, irregular optical surfaces such as large angle diffusers with no specular components and only diffuse components. It would be highly advantageous to provide a roll-to-roll microreplication system capable of fabricating accurate replications of patterns having relief structures from as small as 3μ meters to as large as 100μ meters.